All modern engines work on the principle of Internal Combustion. It is valid for any automobile ranging from heavy buses to even the motorbike you have at home. So what is the principle of Internal Combustion? According to this phenomenon, if you were to combust a small quantity of fuel such as petrol or diesel under high pressure, there would be a tremendous release of energy. It is this energy used to propel our automobiles.
A camshaft is generally a rotating metal rod with oblong cams used to convert rotary motion to reciprocating motion. For internal combustion to occur, there are necessarily four stages — or strokes — that need to be fulfilled. The four strokes of an IC engine are the Intake, Compression, Combustion, and Exhaust strokes.
To ensure the un-interrupted entry and release of air and fuel mixture from the engine, we need a set of intake and exhaust valves. The best mileage bikes all have perfectly tuned cams and valves. Generally, there is a pair of each for each piston of the engine. The camshaft regulates the timing of these valves. Each rotation of the camshaft pushes and retracts the valves, thereby opening/closing the intake and exhaust valves. The tuning of the camshaft and the valves is fundamental to getting the best performance from your bike.
SOHC is an abbreviation for the term Single OverHead Camshaft setup. Primarily, when a single camshaft controls the opening and closing of both the intake and exhaust valves, then the configuration is referred to as a SOHC setup.
On the other hand, if there are two dedicated camshafts, one to regulate the opening of the intake valves and the other to adjust the opening of the exhaust valves, this setup is referred to as a DOHC.
Both of these camshaft arrangements have their pros and cons. However, there are individual differences between SOHC vs. DOHC that you should be aware of:
DOHC engines allow more intake and release of the air-fuel mixture than a SOHC arrangement. It enables the engine to be more powerful and gives you a better pickup. In simpler terms, a DOHC engine can produce more horsepower than a SOHC engine with the same displacement.
Because the DOHC setup allows a smooth implementation of higher valve configurations, this means that the engine can complete more cycles within the same period. It will, in effect, allow valves to be placed in a manner that maximizes performance. Due to this, the top-end power produced by the engine is far higher than that created by a similar SOHC engine.
A SOHC setup generally uses 2 or 3 valves per cylinder. As a result of this, between the two, a SOHC setup is lighter than the DOHC setup. It is because DOHC valves are lighter than SOHC valves.
Because a SOHC engine is lighter, it can produce more torque than a similar DOHC engine at the lower ends. It means that SOHC bikes are generally the best mileage bikes.
The camshaft setup for a bike is an important thing to consider when looking to buy a motorcycle. It is because the power and torque output depend significantly on the arrangement. If you are looking to buy a bike that can produce a lot of horsepower at high revs, then a bike engine with a DOHC configuration would be ideal. Otherwise, a standard SOHC setup would suit your needs.